Convert Base64 data URLs to File objects for Trix attachments

attachment-utils.js

window.AttachmentUtils = (function() {

  var BASE64_MARKER = ';base64,';

  var Utils = {

    // Takes a file size (in bytes) and returns a human-friendly string representation.
    humanFileSize: function(size) {
      if(size < 1) return "0 bytes";
      // http://stackoverflow.com/a/20732091
      var factor = 1000; // Technically it should be 1024, but looks like most apps use 1000...
      var i = Math.floor( Math.log(size) / Math.log(factor) );
      return ( size / Math.pow(factor, i) ).toFixed(1) * 1 + ' ' + ['B', 'kB', 'MB', 'GB', 'TB'][i];
    },

    // Does the given URL (string) look like a base64-encoded URL?
    isDataURI: function(url) {
      return url.split(BASE64_MARKER).length === 2;
    },

    // Converts a data URI string into a File object.
    dataURItoFile: function(dataURI) {
      if(!AttachmentUtils.isDataURI(dataURI)) { return false; }

      // Format of a base64-encoded URL:
      // data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAYAAAAEOCAIAAAAPH1dAAAAK
      var mime = dataURI.split(BASE64_MARKER)[0].split(':')[1];
      var filename = 'dataURI-file-' + (new Date()).getTime() + '.' + mime.split('/')[1];
      var bytes = atob(dataURI.split(BASE64_MARKER)[1]);
      var writer = new Uint8Array(new ArrayBuffer(bytes.length));

      for (var i=0; i < bytes.length; i++) {
        writer[i] = bytes.charCodeAt(i);
      }

      return new File([writer.buffer], filename, { type: mime });
    }

  };

  return Utils;

})();

trix-editor.js

$(function() {

  $(document).on('trix-attachment-add', function(event) {
    var attachment = event.originalEvent.attachment,
        url = attachment.getURL();
    
    // Convert data URLs to File objects.
    if(!attachment.file && AttachmentUtils.isDataURI(url)) {
      attachment.file = AttachmentUtils.dataURItoFile(url);
    }

    if(attachment.file) {
      return uploadAttachment(attachment);
    } else {
      console.error('Could not upload attachment.');
      console.error(attachment);
      attachment.remove();
    }
  });

});

Thank you for this! This solution was exactly what I was looking for.

Nice gist, but I am having errors at uploadAttachment() method, uploadAttachment is not defined. Where is this method at and what's inside it?